U.S. patent application number 16/373448 was filed with the patent office on 2019-10-31 for anodic stimulation in an implantable stimulator system using asymmetric anodic and cathodic stimulation pulses.
The applicant listed for this patent is Boston Scientific Neuromodulation Corporation. Invention is credited to Stephen Carcieri, Goran N. Marnfeldt, Michael A. Moffitt.
Application Number | 20190329039 16/373448 |
Document ID | / |
Family ID | 66175549 |
Filed Date | 2019-10-31 |
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United States Patent
Application |
20190329039 |
Kind Code |
A1 |
Marnfeldt; Goran N. ; et
al. |
October 31, 2019 |
Anodic Stimulation in an Implantable Stimulator System Using
Asymmetric Anodic and Cathodic Stimulation Pulses
Abstract
Recognizing that anodic stimulation may require higher
amplitudes or charge than cathodic stimulation in some tissues, new
pulsing waveforms for a stimulator device, and particularly useful
during monopolar stimulation, are described employing
therapeutically-effective anodic and cathodic stimulation pulses at
the lead-based electrode(s). The pulses are monophasic, with the
amplitude or charge of the anodic monophasic pulses being higher
than the cathodic monophasic pulses. To provide charge balance at
each electrode, a pulse packet may be defined having a plurality of
cathodic monophasic pulses and perhaps only a single anodic
monophasic pulse. Because the polarity of cathodic monophasic
pulses in each packet may charge balance with the anodic monophasic
pulse(s), active charge recovery such as by the use of biphasic
pulses may not be necessary, although passive charge recovery can
be used if desired.
Inventors: |
Marnfeldt; Goran N.;
(Valencia, CA) ; Moffitt; Michael A.; (Saugus,
CA) ; Carcieri; Stephen; (Los Angeles, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Boston Scientific Neuromodulation Corporation |
Valencia |
CA |
US |
|
|
Family ID: |
66175549 |
Appl. No.: |
16/373448 |
Filed: |
April 2, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62663794 |
Apr 27, 2018 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61N 1/0534 20130101;
A61N 1/36196 20130101; A61N 1/36164 20130101; A61N 1/36103
20130101; A61N 1/36178 20130101; A61N 1/36192 20130101; A61N 1/0551
20130101 |
International
Class: |
A61N 1/36 20060101
A61N001/36 |
Claims
1. A stimulator device, comprising: a plurality of electrode nodes,
each electrode node configured to be coupled to one of a plurality
of electrodes configured to contact a patient's tissue; and
stimulation circuitry configured to provide a repeating packet of
pulses at at least two of the electrode nodes selected to create a
stimulation current through the patient's tissue, wherein the
pulses in each packet at at least one of the at least two electrode
nodes comprise at least one monophasic anodic pulse and a plurality
of monophasic cathodic pulses, wherein the at least one monophasic
anodic pulse comprises a first amplitude, and wherein the plurality
of monophasic cathodic pulses each comprise an amplitude less than
the first amplitude.
2. The stimulator device of claim 1, wherein the at least one
monophasic anodic pulse and the plurality of monophasic cathodic
pulses in each packet are separated by gaps during which the
stimulation current is not created through the patient's
tissue.
3. The stimulator device of claim 1, wherein the amplitudes of the
plurality of monophasic cathodic pulses are equal in each
packet.
4. The stimulator device of claim 1, wherein each packet comprises
only the at least one monophasic anodic pulse and the plurality of
monophasic cathodic pulses.
5. The stimulator device of claim 1, wherein the at least one
monophasic anodic pulse and the plurality of monophasic cathodic
pulses in each packet are charge balanced at each of the at least
one electrodes.
6. The stimulator device of claim 1, wherein the at least one
monophasic anodic pulse and the plurality of monophasic cathodic
pulses in each packet are not charge balanced at each of the at
least one electrodes.
7. The stimulator device of claim 1, wherein the pulses in each of
the packets comprise a single monophasic anodic pulse and a
plurality of monophasic cathodic pulses.
8. The stimulator device of claim 1, wherein each packet further
comprises a passive charge recovery phase, wherein during the
passive charge recovery phase the stimulation circuitry is
configured to short the at least two of the electrode nodes to a
reference voltage.
9. The stimulator device of claim 1, wherein the first amplitude of
the at least one monophasic anodic pulse and each amplitude of the
plurality of monophasic cathodic pulses are selected to be
therapeutically effective to recruit neural elements in the
patient's tissue.
10. The stimulator device of claim 1, wherein the first amplitude
of the at least one monophasic anodic pulse is selected to be
therapeutically effective to recruit neural elements in the
patient's tissue, but wherein each amplitude of the plurality of
monophasic cathodic pulses is selected to not be therapeutically
effective to recruit neural elements in the patient's tissue.
11. The stimulator device of claim 1, wherein the at least one
monophasic anodic pulse comprises a passive monophasic anodic
pulse, wherein the stimulation circuitry is configured to provide
the passive monophasic anodic pulse by shorting the at least two of
the electrode nodes to a reference voltage.
12. The stimulator device of claim 1, wherein the stimulation
circuitry is configured to provide the at least one monophasic
anodic pulse and the plurality of monophasic cathodic pulses at a
constant frequency at each of the at least two of the electrode
nodes.
13. The stimulator device of claim 1, further comprising a case for
housing the stimulation circuitry, wherein the case is conductive,
and wherein the conductive case comprises one of the plurality of
electrodes.
14. The stimulator device of claim 13, wherein one of the at least
two of the electrode nodes comprises an electrode node coupled to
the conductive case.
15. The stimulator device of claim 14, further comprising at least
one implantable lead wherein some of the electrodes are located on
the at least one implantable lead.
16. The stimulator device of claim 15, wherein the at least one of
the at least two electrode nodes comprises an electrode node
coupled to an electrode located on the at least one implantable
lead.
17. The stimulator device of claim 1, wherein each electrode node
is coupled to an electrode through a DC-blocking capacitor.
18. The stimulator device of claim 1, wherein the first amplitude
of the at least one monophasic anodic pulse and each amplitude of
the plurality of monophasic cathodic pulses comprise constant
current amplitudes.
19. The stimulator device of claim 1, wherein the pulses in each
packet at at least one other of the at least two electrode nodes
comprise at least one monophasic cathodic pulse corresponding in
time to the at least one monophasic anodic pulse and a plurality of
monophasic anodic pulses each corresponding in time to one of the
plurality of monophasic cathodic pulses, wherein the at least one
monophasic cathodic pulse comprises the first amplitude, and
wherein each of the plurality of monophasic anodic pulses comprises
the amplitude of its corresponding monophasic cathodic pulse.
20. The stimulator device of claim 1, wherein the at least one
monophasic anodic pulse and the plurality of monophasic cathodic
pulses are charge imbalanced at each of the at least one electrodes
in a plurality of the packets, but wherein the charge is balanced
at each of the at least one electrodes over a duration of the
plurality of the packets.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is a non-provisional application of U.S. Provisional
Patent Application Ser. No. 62/663,794, filed Apr. 27, 2018, to
which priority is claimed, and which is incorporated herein by
reference in its entirety.
FIELD OF THE INVENTION
[0002] This application relates to Implantable Pulse Generators
(IPGs), and more specifically to circuitry and methods for using
anodic stimulation using asymmetric stimulation pulses.
INTRODUCTION
[0003] Implantable neurostimulator devices are devices that
generate and deliver electrical stimuli to body nerves and tissues
for the therapy of various biological disorders, such as pacemakers
to treat cardiac arrhythmia, defibrillators to treat cardiac
fibrillation, cochlear stimulators to treat deafness, retinal
stimulators to treat blindness, muscle stimulators to produce
coordinated limb movement, spinal cord stimulators to treat chronic
pain, cortical and deep brain stimulators to treat motor and
psychological disorders, and other neural stimulators to treat
urinary incontinence, sleep apnea, shoulder subluxation, etc. The
description that follows will generally focus on the use of the
invention within a Deep Brain Stimulation (DBS) or Spinal Cord
Stimulation (SCS) system, such as that disclosed in U.S. Pat. No.
6,516,227 and U.S. Patent Application Publication 2016/0184591.
However, the present invention may find applicability with any
implantable neurostimulator device system.
[0004] An SCS or DBS system typically includes an Implantable Pulse
Generator (IPG) 10 shown in FIG. 1. The IPG 10 includes a
biocompatible device case 12 that holds the circuitry and a battery
14 for providing power for the IPG to function. The IPG 10 is
coupled to tissue-stimulating electrodes 16 via one or more
electrode leads that form an electrode array 17. For example, one
or more percutaneous leads 15 can be used having ring-shaped or
split-ring electrodes 16 carried on a flexible body 18. In another
example, a paddle lead 19 provides electrodes 16 positioned on one
of its generally flat surfaces. Lead wires 20 within the leads are
coupled to the electrodes 16 and to proximal contacts 21 insertable
into lead connectors 22 fixed in a header 23 on the IPG 10, which
header can comprise an epoxy for example. Once inserted, the
proximal contacts 21 connect to header contacts 24 within the lead
connectors 22, which are in turn coupled by feedthrough pins 25
through a case feedthrough 26 to stimulation circuitry 28 within
the case 12, which stimulation circuitry 28 is described below.
[0005] In the illustrated IPG 10, there are thirty-two electrodes
(E1-E32), split between four percutaneous leads 15, or contained on
a single paddle lead 19, and thus the header 23 may include a
2.times.2 array of eight-electrode lead connectors 22. However, the
type and number of leads, and the number of electrodes, in an IPG
is application specific and therefore can vary. The conductive case
12 can also comprise an electrode (Ec).
[0006] In a SCS application, as is useful to alleviate chronic back
pain for example, the electrode lead(s) are typically implanted in
the spinal column proximate to the dura in a patient's spinal cord,
preferably spanning left and right of the patient's spinal column.
The proximal contacts 21 are tunneled through the patient's tissue
to a distant location such as the buttocks where the IPG case 12 is
implanted, at which point they are coupled to the lead connectors
22. In a DBS application, as is useful in the treatment of tremor
in Parkinson's disease for example, the IPG 10 is typically
implanted under the patient's clavicle (collarbone). Percutaneous
leads 15 are tunneled through the neck and the scalp where the
electrodes 16 are implanted through holes drilled in the skull and
positioned for example in the subthalamic nucleus (STN) and the
pedunculopontine nucleus (PPN) in each brain hemisphere. In other
IPG examples designed for implantation directly at a site requiring
stimulation, the IPG can be lead-less, having electrodes 16 instead
appearing on the body of the IPG 10. The IPG lead(s) can be
integrated with and permanently connected to the IPG 10 in other
solutions.
[0007] IPG 10 can include an antenna 27a allowing it to communicate
bi-directionally with a number of external devices discussed
subsequently. Antenna 27a as shown comprises a conductive coil
within the case 12, although the coil antenna 27a can also appear
in the header 23. When antenna 27a is configured as a coil,
communication with external devices preferably occurs using
near-field magnetic induction. IPG 10 may also include a
Radio-Frequency (RF) antenna 27b. In FIG. 1, RF antenna 27b is
shown within the header 23, but it may also be within the case 12.
RF antenna 27b may comprise a patch, slot, or wire, and may operate
as a monopole or dipole. RF antenna 27b preferably communicates
using far-field electromagnetic waves, and may operate in
accordance with any number of known RF communication standards,
such as Bluetooth, Zigbee, WiFi, MICS, and the like.
[0008] Stimulation in IPG 10 is typically provided by pulses each
of which may include a number of phases such as 30a and 30b, as
shown in the example of FIG. 2A. In the example shown, such
stimulation is monopolar, meaning that a current is provided
between at least one selected lead-based electrode (e.g., E1) and
the case electrode Ec 12. Stimulation parameters typically include
amplitude (current I, although a voltage amplitude V can also be
used); frequency (f); pulse width (PW) of the pulses or of its
individual phases such as 30a and 30b ; the electrodes 16 selected
to provide the stimulation; and the polarity of such selected
electrodes, i.e., whether they act as anodes that source current to
the tissue or cathodes that sink current from the tissue. These and
possibly other stimulation parameters taken together comprise a
stimulation program that the stimulation circuitry 28 in the IPG 10
can execute to provide therapeutic stimulation to a patient.
[0009] In the example of FIG. 2A, electrode E1 has been selected as
a cathode (during its first phase 30a), and thus provides pulses
which sink a negative current of amplitude -I from the tissue. The
case electrode Ec has been selected as an anode (again during first
phase 30a), and thus provides pulses which source a corresponding
positive current of amplitude +I from the tissue. Note that at any
time the current sunk from the tissue (e.g., -I at E1 during phase
30a) equals the current sourced to the tissue (e.g., +I at Ec
during phase 30a) to ensure that the net current injected into the
tissue is zero.
[0010] IPG 10 as mentioned includes stimulation circuitry 28 to
form prescribed stimulation at a patient's tissue. FIG. 3 shows an
example of stimulation circuitry 28, which includes one or more
current sources 40, and one or more current sinks 42.sub.i. The
sources and sinks 40.sub.i and 42.sub.i can comprise
Digital-to-Analog converters (DACs), and may be referred to as
PDACs 40.sub.I and NDACs 42.sub.I in accordance with the Positive
(sourced, anodic) and Negative (sunk, cathodic) currents they
respectively issue. In the example shown, a NDAC/PDAC
40.sub.i/42.sub.i pair is dedicated (hardwired) to a particular
electrode node ei 39. Each electrode node ei 39 is connected to an
electrode Ei 16 via a DC-blocking capacitor Ci 38, for the reasons
explained below. PDACs 40, and NDACs 42.sub.i can also comprise
voltage sources.
[0011] Proper control of the PDACs 40.sub.i and NDACs 42.sub.i
allows any of the electrodes 16 and the case electrode Ec 12 to act
as anodes or cathodes to create a current through a patient's
tissue, R, hopefully with good therapeutic effect. In the example
shown, and consistent with the first pulse phase 30a of FIG. 2A,
electrode E1 has been selected as a cathode electrode to sink
current from the tissue R and case electrode Ec has been selected
as an anode electrode to source current to the tissue R. Thus PDAC
40.sub.C and NDAC 42.sub.1 are activated and digitally programmed
to produce the desired current, I, with the correct timing (e.g.,
in accordance with the prescribed frequency F and pulse width PW).
Power for the stimulation circuitry 28 is provided by a compliance
voltage VH, as described in further detail in U.S. Patent
Application Publication 2013/0289665.
[0012] Other stimulation circuitries 28 can also be used in the IPG
10. In an example not shown, a switching matrix can intervene
between the one or more PDACs 40.sub.i and the electrode nodes ei
39, and between the one or more NDACs 42.sub.i and the electrode
nodes. Switching matrices allows one or more of the PDACs or one or
more of the NDACs to be connected to one or more electrode nodes at
a given time. Various examples of stimulation circuitries can be
found in U.S. Pat. Nos. 6,181,969, 8,606,362, 8,620,436, U.S.
patent application Ser. No. 15/695,965, filed Sep. 5, 2017, and
U.S. Provisional Patent Application Ser. No. 62/559,247, filed Sep.
15, 2017.
[0013] Much of the stimulation circuitry 28 of FIG. 3, including
the PDACs 40.sub.i and NDACs 42.sub.i, the switch matrices (if
present), and the electrode nodes ei 39 can be integrated on one or
more Application Specific Integrated Circuits (ASICs), as described
in U.S. Patent Application Publications 2012/0095529, 2012/0092031,
and 2012/0095519. As explained in these references, ASIC(s) may
also contain other circuitry useful in the IPG 10, such as
telemetry circuitry (for interfacing off chip with telemetry
antennas 27a and/or 27b), circuitry for generating the compliance
voltage VH, various measurement circuits, etc.
[0014] Also shown in FIG. 3 are DC-blocking capacitors Ci 38 placed
in series in the electrode current paths between each of the
electrode nodes ei 39 and the electrodes Ei 16 (including the case
electrode Ec 12). The DC-blocking capacitors 38 act as a safety
measure to prevent DC current injection into the patient, as could
occur for example if there is a circuit fault in the stimulation
circuitry 28. The DC-blocking capacitors 38 are typically provided
off-chip (off of the ASIC(s)), and instead may be provided in or on
a circuit board in the IPG 10 used to integrate its various
components, as explained in U.S. Patent Application Publication
2015/0157861.
[0015] Referring again to FIG. 2A, the stimulation pulses as shown
are biphasic, with each pulse comprising a first phase 30a followed
thereafter by a second phase 30b of opposite polarity. Biphasic
pulses are useful to actively recover any charge that might be
stored on capacitive elements in the electrode current paths, such
as on the DC-blocking capacitors 38. Charge recovery is shown with
reference to both FIGS. 2A and 2B. During the first pulse phase
30a, charge will build up across the DC-blockings capacitors C1 and
Cc associated with the electrodes E1 and Ec used to produce the
current, giving rise to voltages Vc1 and Vcc which decrease in
accordance with the amplitude of the current and the capacitance of
the capacitors 38 (dV/dt=I/C). During the second pulse phase 30b,
when the polarity of the current I is reversed at the selected
electrodes E1 and Ec, the stored charge on capacitors C1 and Cc is
actively recovered, and thus voltages Vc1 and Vcc increase and
return to 0V at the end the second pulse phase 30b.
[0016] To recover all charge by the end of the second pulse phase
30b of each pulse (Vc1=Vcc=0V), the first and second phases 30a and
30b are charged balanced at each electrode, with the first pulse
phase 30a providing a charge of -Q (-I*PW) and the second pulse
phase 30b providing a charge of +Q (+I*PW) at electrode E1, and
with the first pulse phase 30a providing a charge of +Q and the
second pulse phase 30b providing a charge of -Q at the case
electrode Ec. In the example shown, such charge balancing is
achieved by using the same pulse width (PW) and the same amplitude
(|I|) for each of the opposite-polarity pulse phases 30a and 30b.
However, the pulse phases 30a and 30b may also be charged balance
if the product of the amplitude and pulse widths of the two phases
30a and 30b are equal, or if the area under each of the phases is
equal, as is known.
[0017] FIG. 3 shows that stimulation circuitry 28 can include
passive recovery switches 41.sub.i, which are described further in
U.S. Patent Application Publications 2018/0071527 and 2018/0140831.
Passive recovery switches 41.sub.i may be attached to each of the
electrode nodes ei 39, and are used to passively recover any charge
remaining on the DC-blocking capacitors Ci 38 after issuance of the
second pulse phase 30b--i.e., to recover charge without actively
driving a current using the DAC circuitry. Passive charge recovery
can be prudent, because non-idealities in the stimulation circuitry
28 may lead to pulse phases 30a and 30b that are not perfectly
charge balanced.
[0018] Therefore, and as shown in FIG. 2A, passive charge recovery
typically occurs after the issuance of second pulse phases 30b, for
example during at least a portion 30c of the quiet periods between
the pulses, by closing passive recovery switches 41.sub.i. As shown
in FIG. 3, the other end of the switches 41.sub.i not coupled to
the electrode nodes ei 39 are connected to a common reference
voltage, which in this example comprises the voltage of the battery
14, Vbat, although another reference voltage could be used. As
explained in the above-cited references, passive charge recovery
tends to equilibrate the charge on the DC-blocking capacitors 38 by
placing the capacitors in parallel between the reference voltage
(Vbat) and the patient's tissue. Note that passive charge recovery
is illustrated as small exponentially-decaying curves during 30c in
FIG. 2A, which may be positive or negative depending on whether
pulse phase 30a or 30b have a predominance of charge at a given
electrode.
[0019] Passive charge recovery 30c may alleviate the need to use
biphasic pulses for charge recovery, especially in the DBS context
when the amplitudes of currents may be lower, and therefore charge
recovery less of a concern. For example, and although not shown in
FIG. 2A, the pulses provided to the tissue may be monophasic,
comprising only a first pulse phase 30a. This may be followed
thereafter by passive charge recovery 30c to eliminate any charge
build up that occurred during the singular pulses 30a.
[0020] FIG. 4 shows an external trial stimulation environment that
may precede implantation of an IPG 10 in a patient, particularly in
an SCS application. During external trial stimulation, stimulation
can be tried on a prospective implant patient without going so far
as to implant the IPG 10. Instead, one or more trial electrode
arrays 17' (e.g., one or more trial percutaneous leads 15 or trial
paddle leads 19) are implanted in the patient's tissue at a target
location 52, such as within the spinal column as explained earlier.
The proximal ends of the trial electrode array(s) 17' exit an
incision 54 in the patient's tissue and are connected to an
External Trial Stimulator (ETS) 50. The ETS 50 generally mimics
operation of the IPG 10, and thus can provide stimulation to the
patient's tissue as explained above. See, e.g., U.S. Pat. No.
9,259,574, disclosing a design for an ETS. The ETS 50 is generally
worn externally by the patient for a short while (e.g., two weeks),
which allows the patient and his clinician to experiment with
different stimulation parameters to hopefully find a stimulation
program that alleviates the patient's symptoms (e.g., pain). If
external trial stimulation proves successful, the trial electrode
array(s) 17' are explanted, and a full IPG 10 and a permanent
electrode array 17 (e.g., one or more percutaneous 15 or paddle 19
leads) are implanted as described above; if unsuccessful, the trial
electrode array(s) 17' are simply explanted.
[0021] Like the IPG 10, the ETS 50 can include one or more antennas
to enable bi-directional communications with external devices such
as those shown in FIG. 5. Such antennas can include a near-field
magnetic-induction coil antenna 56a, and/or a far-field RF antenna
56b, as described earlier. ETS 50 may also include stimulation
circuitry able to form stimulation in accordance with a stimulation
program, which circuitry may be similar to or comprise the same
stimulation circuitry 28 (FIG. 3) present in the IPG 10. ETS 50 may
also include a battery (not shown) for operational power.
[0022] FIG. 5 shows various external devices that can wirelessly
communicate data with the IPG 10 or ETS 50, including a patient,
hand-held external controller 60, and a clinician programmer 70.
Both of devices 60 and 70 can be used to wirelessly transmit a
stimulation program to the IPG 10 or ETS 50--that is, to program
their stimulation circuitries to produce stimulation with a desired
amplitude and timing described earlier. Both devices 60 and 70 may
also be used to adjust one or more stimulation parameters of a
stimulation program that the IPG 10 is currently executing. Devices
60 and 70 may also wirelessly receive information from the IPG 10
or ETS 50, such as various status information, etc.
[0023] External controller 60 can be as described in U.S. Patent
Application Publication 2015/0080982 for example, and may comprise
a controller dedicated to work with the IPG 10 or ETS 50. External
controller 60 may also comprise a general purpose mobile
electronics device such as a mobile phone which has been programmed
with a Medical Device Application (MDA) allowing it to work as a
wireless controller for the IPG 10 or ETS, as described in U.S.
Patent Application Publication 2015/0231402. External controller 60
includes a user interface, preferably including means for entering
commands (e.g., buttons or selectable graphical elements) and a
display 62. The external controller 60's user interface enables a
patient to adjust stimulation parameters, although it may have
limited functionality when compared to the more-powerful clinician
programmer 70, described shortly.
[0024] The external controller 60 can have one or more antennas
capable of communicating with the IPG 10. For example, the external
controller 60 can have a near-field magnetic-induction coil antenna
64a capable of wirelessly communicating with the coil antenna 27a
or 56a in the IPG 10 or ETS 50. The external controller 60 can also
have a far-field RF antenna 64b capable of wirelessly communicating
with the RF antenna 27b or 56b in the IPG 10 or ETS 50.
[0025] Clinician programmer 70 is described further in U.S. Patent
Application Publication 2015/0360038, and can comprise a computing
device 72, such as a desktop, laptop, or notebook computer, a
tablet, a mobile smart phone, a Personal Data Assistant (PDA)-type
mobile computing device, etc. In FIG. 5, computing device 72 is
shown as a laptop computer that includes typical computer user
interface means such as a screen 74, a mouse, a keyboard, speakers,
a stylus, a printer, etc., not all of which are shown for
convenience. Also shown in FIG. 5 are accessory devices for the
clinician programmer 70 that are usually specific to its operation
as a stimulation controller, such as a communication "wand" 76
coupleable to suitable ports on the computing device 72, such as
USB ports 79 for example.
[0026] The antenna used in the clinician programmer 70 to
communicate with the IPG 10 or ETS 50 can depend on the type of
antennas included in those devices. If the patient's IPG 10 or ETS
50 includes a coil antenna 27a or 56a, wand 76 can likewise include
a coil antenna 80a to establish near-filed magnetic-induction
communications at small distances. In this instance, the wand 76
may be affixed in close proximity to the patient, such as by
placing the wand 76 in a belt or holster wearable by the patient
and proximate to the patient's IPG 10 or ETS 50. If the IPG 10 or
ETS 50 includes an RF antenna 27b or 56b, the wand 76, the
computing device 72, or both, can likewise include an RF antenna
80b to establish communication at larger distances. The clinician
programmer 70 can also communicate with other devices and networks,
such as the Internet, either wirelessly or via a wired link
provided at an Ethernet or network port.
[0027] To program stimulation programs or parameters for the IPG 10
or ETS 50, the clinician interfaces with a clinician programmer
graphical user interface (GUI) 82 provided on the display 74 of the
computing device 72. As one skilled in the art understands, the GUI
82 can be rendered by execution of clinician programmer software 84
stored in the computing device 72, which software may be stored in
the device's non-volatile memory 86. Execution of the clinician
programmer software 84 in the computing device 72 can be
facilitated by control circuitry 88 such as one or more
microprocessors, microcomputers, FPGAs, DSPs, other digital logic
structures, etc., which are capable of executing programs in a
computing device, and which may comprise their own memories. For
example, control circuitry 88 can comprise an i5 processor
manufactured by Intel Corp, as described at
https://www.intel.com/content/www/us/en/products/processors/core/i5-proce-
ssors.html. Such control circuitry 88, in addition to executing the
clinician programmer software 84 and rendering the GUI 82, can also
enable communications via antennas 80a or 80b to communicate
stimulation parameters chosen through the GUI 82 to the patient's
IPG 10.
[0028] The user interface of the external controller 60 may provide
similar functionality because the external controller 60 can
include the same hardware and software programming as the clinician
programmer. For example, the external controller 60 includes
control circuitry 66 similar to the control circuitry 88 in the
clinician programmer 70, and may similarly be programmed with
external controller software stored in device memory.
SUMMARY
[0029] A stimulator device, which may comprise: a plurality of
electrode nodes, each electrode node configured to be coupled to
one of a plurality of electrodes configured to contact a patient's
tissue; and stimulation circuitry configured to provide a repeating
packet of pulses at at least two of the electrode nodes selected to
create a stimulation current through the patient's tissue, wherein
the pulses in each packet at at least one of the at least two
electrode nodes comprise at least one monophasic anodic pulse and a
plurality of monophasic cathodic pulses, wherein the at least one
monophasic anodic pulse comprises a first amplitude or charge, and
wherein the plurality of monophasic cathodic pulses each comprise
an amplitude or charge less than the first amplitude or charge.
[0030] The at least one monophasic anodic pulse and the plurality
of monophasic cathodic pulses in each packet may be separated by
gaps during which the stimulation current is not created through
the patient's tissue. The amplitudes or charges of the plurality of
monophasic cathodic pulses may be equal in each packet. Each packet
may comprises only the at least one monophasic anodic pulse and the
plurality of monophasic cathodic pulses.
[0031] The at least one monophasic anodic pulse and the plurality
of monophasic cathodic pulses in each packet may or may not be
charge balanced at each of the at least one electrodes. The pulses
in each of the packets may comprise a single monophasic anodic
pulse and a plurality of monophasic cathodic pulses. Each packet
may further comprise a passive charge recovery phase, wherein
during the passive charge recovery phase the stimulation circuitry
is configured to short the at least two of the electrode nodes to a
reference voltage.
[0032] The first amplitude or charge of the at least one monophasic
anodic pulse and each amplitude or charge of the plurality of
monophasic cathodic pulses may be selected to be therapeutically
effective to recruit neural elements in the patient's tissue.
Alternatively, the first amplitude or charge of the at least one
monophasic anodic pulse may be selected to be therapeutically
effective to recruit neural elements in the patient's tissue, but
each amplitude or charge of the plurality of monophasic cathodic
pulses may be selected to not be therapeutically effective to
recruit neural elements in the patient's tissue.
[0033] The at least one monophasic anodic pulse may comprise a
passive monophasic anodic pulse, wherein the stimulation circuitry
is configured to provide the passive monophasic anodic pulse by
shorting the at least two of the electrode nodes to a reference
voltage. The stimulation circuitry may be configured to provide the
at least one monophasic anodic pulse and the plurality of
monophasic cathodic pulses at a constant frequency at each of the
at least two of the electrode nodes.
[0034] The stimulator device may further comprise a case for
housing the stimulation circuitry, wherein the case is conductive,
and wherein the conductive case comprises one of the plurality of
electrodes. One of the at least two of the electrode nodes may
comprise an electrode node coupled to the conductive case. The
stimulator device may further comprise at least one implantable
lead wherein some of the electrodes are located on the at least one
implantable lead. The at least one of the at least two electrode
nodes may comprise an electrode node coupled to an electrode
located on the at least one implantable lead.
[0035] Each electrode node may be coupled to an electrode through a
DC-blocking capacitor. The first amplitude of the at least one
monophasic anodic pulse and each amplitude of the plurality of
monophasic cathodic pulses may comprise constant current
amplitudes.
[0036] The stimulator device may comprise an implantable pulse
generator, such as a deep brain stimulator. The stimulator device
may also comprise an external stimulator.
[0037] The pulses in each packet at at least one other of the at
least two electrode nodes may comprise at least one monophasic
cathodic pulse corresponding in time to the at least one monophasic
anodic pulse and a plurality of monophasic anodic pulses each
corresponding in time to one of the plurality of monophasic
cathodic pulses, wherein the at least one monophasic cathodic pulse
comprises the first amplitude or charge, and wherein each of the
plurality of monophasic anodic pulses comprises the amplitude or
charge of its corresponding monophasic cathodic pulse.
[0038] The at least one monophasic anodic pulse and the plurality
of monophasic cathodic pulses may be charge imbalanced at each of
the at least one electrodes in a plurality of the packets, but the
charge may be balanced at each of the at least one electrodes over
a duration of the plurality of the packets.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] FIG. 1 shows an Implantable Pulse Generator (IPG), in
accordance with the prior art.
[0040] FIGS. 2A and 2B show an example of stimulation pulses
(waveforms) producible by the IPG or by an External Trial
Stimulator (ETS), in accordance with the prior art.
[0041] FIG. 3 shows an example of stimulation circuitry useable in
the IPG or ETS, in accordance with the prior art.
[0042] FIG. 4 shows an ETS environment useable to provide
stimulation before implantation of an IPG, in accordance with the
prior art.
[0043] FIG. 5 shows various external devices capable of
communicating with and programming stimulation in an IPG or ETS, in
accordance with the prior art.
[0044] FIGS. 6 shows biphasic waveforms producible by an IPG or ETS
having an anodic first pulse phase at a lead-based electrode and
useable during monopolar stimulation using the case electrode as a
return.
[0045] FIG. 7A shows an example of waveforms producible by an IPG
or ETS having a repeating packet of pulses, with each packet
including a high amplitude monophasic anodic pulse followed by a
plurality of lower amplitude monophasic cathodic pulses, where the
pulses are charge balanced at each electrode.
[0046] FIGS. 7B and 7C show other examples of waveforms similar to
FIG. 7A in which the anodic and cathodic pulses are ordered
differently inside each packet.
[0047] FIG. 8 shows another example of waveforms in which the
cathodic pulses have the same charge but are shaped differently by
varying their amplitudes or pulse widths.
[0048] FIG. 9 shows another example of waveforms in which the
cathodic pulses have differing amounts of charge.
[0049] FIG. 10 shows another example of waveforms having more than
one anodic pulse in addition to the cathodic pulses.
[0050] FIG. 11 shows another example of waveforms in which two
lead-based electrodes are selected along with the case electrode
during monophasic stimulation.
[0051] FIG. 12 shows another example of waveforms in which the
anodic pulse is passively formed using passive recovery circuitry
in the IPG or ETS.
[0052] FIG. 13 shows another example of waveforms in which the
anodic and cathodic pulses are formed at two lead-based electrodes
using bipolar stimulation.
[0053] FIG. 14 shows another example of waveforms in which only the
anodic pulse is therapeutically effective, and in which the
cathodic pulses are not therapeutically effective but are instead
used for charge recovery.
[0054] FIG. 15 shows another example of waveforms in which the
anodic and cathodic pulses do not occur at a constant
frequency.
[0055] FIG. 16 shows another example of waveforms with each packet
including a high amplitude monophasic cathodic pulse followed by a
plurality of lower amplitude monophasic anodic pulses, where the
pulses are charge balanced at each electrode.
[0056] FIG. 17 shows another example of waveforms in which the
anodic and cathodic pulses are charge imbalanced at each electrode
in each packet.
[0057] FIG. 18 shows another example of waveforms in which the
anodic and cathodic pulses are charge imbalanced at each electrode
in each packet, but where different packets are in sum charge
balanced at each electrode.
[0058] FIGS. 19A and 19B show other examples of waveforms in which
charge is imbalanced within the pulse packets to affect a DC
current bias in the tissue.
[0059] FIG. 20 shows a Graphical User Interface (GUI) rendered on
an external device and useable to program an IPG or ETS with any of
the waveforms previously illustrated.
[0060] FIG. 21 shows circuitry in the IPG or ETS for receiving
stimulation parameters as provided by the GUI of the external
device and to provide the specified waveforms.
DETAILED DESCRIPTION
[0061] Especially in the DBS context, monopolar stimulation is
traditionally performed using cathodic stimulation--that is, by
using pulses at the lead-based electrodes (e.g., E1) whose first
(or only) pulse phase 30a is cathodic (negative). As a result, and
to ensure that the net charge injection into the tissue at any time
is zero, the corresponding first (or only) pulse phase 30a at the
case electrode would be anodic (positive). Such traditional
cathodic monopolar stimulation was shown in FIG. 2A via the use of
biphasic pulses, although as described earlier, a single pulse
phase followed by passive recovery may be used as well.
[0062] However, anodic stimulation--that is, using pulses at the
lead-based electrodes whose first (or only) pulse phase 30a is
anodic (positive)--may provide superior results. Anodic monopolar
stimulation is shown in FIG. 6, again using charge-balanced
biphasic pulses. As shown, a lead-based electrode has been selected
(e.g., E1, although any other electrode 16 could be chosen) to
provide stimulation along with the case electrode Ec. To ensure
that there is no net charge injection into the tissue at any given
time, the case electrode Ec is provided with pulse phases of
opposite polarity, i.e., with a cathodic first pulse phase 100a
followed by a charge-balanced anodic second pulse phase 100b. As
described earlier, the second pulse phases 100b can be followed by
a passive recovery phase 100c, during which the passive recovery
switches 41.sub.i (FIG. 3) can be closed to equilibrate any
remaining charge on capacitances in the current path.
[0063] While either a cathodic pulse (FIG. 2A) or an anodic pulse
(FIG. 6) may be effective to provide stimulation to the tissue, the
amplitude of the current needed may vary. For example, to stimulate
the same tissue, the amplitude of an anodic current may need to be
1.5 to 3 times higher than a cathodic current. The charge of an
anodic pulse may also need to be higher than cathodic pulses to
stimulate the same tissue.
[0064] This may make the use of anodic stimulation as depicted in
FIG. 6 difficult. Assume for example that effective anodic
stimulation for a given patient requires an anodic current of
amplitude +I at electrode E1 during the first phase 100a. This
could render the current used during active charge recovery--i.e.,
during the second pulse phase 100b--too high. If the second pulse
phase 100b is assumed to have the same pulse width (PW) as the
first pulse phase 100a, charge balanced at E1 would mandate that
the second pulse phase 100b would also have the same amplitude as
the first pulse phase (although of opposite polarity, -I). A
cathodic current of this amplitude could be 1.5 to 3 times higher
than needed to stimulate the tissue. Thus, even though the second
pulse phase 100b is intended merely as a means of charge recovery
and not as a therapeutically-significant pulse, the cathodic second
pulse phase 100b runs the risk of over-stimulating the tissue. In
fact, the cathodic current in the second pulse phase could be
painful to the patient or create other unwanted side effects.
[0065] Recognizing that anodic stimulation may require higher
amplitudes or charge than cathodic stimulation, new pulsing
waveforms particularly useful during monopolar stimulation are
described employing therapeutically-effective anodic and cathodic
stimulation pulses at the lead-based electrode(s). In some
examples, the pulses are monophasic, with the amplitude or charge
of the anodic monophasic pulses being higher than the cathodic
monophasic pulses. To provide charge balance at each electrode, a
pulse packet may be defined having a plurality of cathodic
monophasic pulses and perhaps only a single anodic monophasic
pulse. Because the polarity of cathodic monophasic pulses in each
packet may charge balance with the anodic monophasic pulse(s),
active charge recovery such as by the use of biphasic pulses may
not be necessary, although passive charge recovery can be used. Use
of both anodic and cathodic currents can be beneficial because such
currents may recruit different neural elements in the patient's
tissue (e.g., cells versus fibers).
[0066] A first example of new pulsing waveforms as just described
is shown in FIG. 7A. The pulses in FIG. 7A are monopolar, with one
or more lead-based electrodes 16 (e.g., E1) and the case electrode
12 Ec selected to provide monopolar stimulation. In this example,
monophasic anodic stimulation pulses 110 and monophasic cathodic
pulses 112 are issued at a frequency f, which frequency has
presumably been found to be effective for the patient. The pulses
are organized in packets 115, and in the example shown each packet
115 comprises at the lead-based electrode E1 a single monophasic
anodic stimulation pulse 110 followed by a plurality (e.g., three)
of monophasic cathodic stimulation pulses 110. To prevent net
charge injection into the tissue at any given time, the pulse
packet 115 at the case electrode Ec comprises pulses 110 and 112 of
the same amplitudes but opposite polarities: a single monophasic
cathodic stimulation pulse 110 followed by a plurality (e.g.,
three) of monophasic anodic stimulation pulses 112. While the
opposite-polarity return electrode Ec is shown in subsequent
figures for completeness, discussion in this disclosure will focus
on the pulses formed at the lead-based electrodes (e.g., E1)
involved in neural recruitment.
[0067] The pulse packets 115 repeat as shown, such that the pulses
110 or 112 issued at the specified frequency, f. Preferably, the
pulses 110 and 112 in each packet 115 are separated by gaps during
which a stimulation current is not created through the patient's
tissue.
[0068] As discussed above, stimulating tissue at a lead-based
electrode E1 may require a higher-amplitude anodic current and a
lower-amplitude cathodic current, and this is reflected in the
amplitudes of the anodic stimulation pulses 110 and 112. In this
example, while the amplitude of the anodic stimulation pulses 110
at E1 are +I, the amplitude of the cathodic stimulation pulses 112
are -1/3I. If an effective anodic current is assumed to be three
times the amplitude of a cathodic current, these pulses 112 and 110
should each be therapeutically effective to recruit the tissue
proximate to electrode E1. Beneficially, the anodic and cathodic
currents may recruit different neural elements in the tissue.
[0069] Beneficially, each of the pulses 110 and 112 comprises a
single phase (i.e., are monophasic) and do not require second
(opposite) pulses phases for the purpose of active charge recovery.
This simplifies the issuance of the pulses, and reduces the amount
of power needed to form the pulses compared to techniques like FIG.
6A that use biphasic pulses. Nonetheless, charge recovery at each
electrode can still occur. This is because each of the cathodic
pulses 112 in a packet 115 may be structured to recover charge
built up by the single anodic pulse 110 over the duration of that
packet. In other words, the cathodic pulses 112 are structured to
provide a total summed charge of -Q while the anodic pulse 110 is
structured to provide a total charge of +Q in each packet.
[0070] Charge balancing can be achieved in different ways, but in
FIG. 7A is achieved by inversely scaling the amplitude of the
cathodic pulses 112 in accordance with the number of those pulses
112 included in each packet 115. Assuming pulses 110 and 112 all
have the same pulse width (PW), and that three cathodic pulses 112
are used, the amplitude of the cathodic pulses are set to -1/3I
(-1/3I) the amplitude of the anodic pulse 110 (+I). The charge of
each cathodic pulse 112 is thus equal to -1/3*I*PW, and thus in sum
equals -Q=-I*PW, which is equal and opposite to the charge +Q=+I*PW
of the anodic pulse 110. In other examples also achieving charge
balance at each electrode, two cathodic pulses 112 may be used in
each packet 115 with amplitudes -1/2I, or four cathodic pulses 112
may be used with amplitudes -1/4I, etc.
[0071] FIG. 7A shows how the pulses 110 and 112 achieve charge
recovery by review of the voltages that build up on capacitances in
the current path, such as on the DC-blocking capacitors 38 (C1 and
Cc) associated with electrode E1 and the case electrode Ec. Charge
will build up during the anodic pulse 110, and Vc1 and Vcc across
C1 and Cc (FIG. 2B) will rise. This charge is recovered during each
subsequent cathodic pulse 112, and eventually Vc1 and Vcc fall back
to zero (117) at the end of the packet 115. In other words, by
charge balancing the sum of the charge of the cathodic pulses 112
to equal the opposite charge of the anodic pulse 112, complete
charge recovery is achieved by the end of the pulse packet 115.
[0072] Passive charge recovery may also be used to ensure complete
charge recovery, because as noted earlier intentional charge
balancing at a given electrode may not be perfect given
non-idealities. In this regard, passive charge recovery periods 114
are included after the last pulse in each packet 115. By way of
review, passive charge recovery occurs by closing at least the
passive recovery switches 41.sub.1 and 41.sub.c (FIG. 3) associated
with the electrodes E1 and Ec chosen for stimulation, which couples
electrode nodes e1 and ec 39 to a common reference voltage (Vbat).
All passive recovery switches 41.sub.i may also be closed during
periods 114 if desired.
[0073] FIGS. 7B and 7C show that the order of the anodic pulse 110
and cathodic pulses 112 in each packet 115 does not matter and can
be modified. Thus, in FIG. 7B, a cathodic pulse 112 occurs first at
E1 in each packet 115, followed by the anodic pulse 110, and
followed by two cathodic pulses 112. In FIG. 7C, the anodic pulse
110 occurs at the end of the packet 115 after all three cathodic
pulses 112. This still arrives at a charge-balanced solution at
each electrode, and again passive charge recovery 114 can be used
after each last pulse in the packet 115. In fact, and recognizing
that the packets 115 repeat and that the order of the pulses 110
and 112 in each packet can vary, passive charge recovery 114 can
actually occur at any set position in the packet 115--after the
first pulse, after the second pulse, etc. Further, passive charge
recovery 114 can also occur after every pulse 110 and 112 if
desired.
[0074] FIG. 8 shows that charge balancing can also be achieved by
varying the pulse widths of the pulses in the packet 115. Three
cathodic pulses 112 are again shown, with each having different
shapes. The first has an amplitude of -1/6I and a pulse width 2PW;
the second has an amplitude -2/3I and a pulse width of 1/2PW; and
the third has an amplitude of -1/3I and a pulse width PW. The
charge of each cathodic pulse 112 is -1/3*I*PW, and so all three in
sum have a charge -Q=-I*PW, equal and opposite to the charge of the
anodic pulse 110, +Q=+I *PW. Although not shown, note that the
pulses 110 and 112 do not need to be square pulses of constant
current amplitudes, but could have random shapes, while still being
charge balanced.
[0075] FIG. 9 shows that charge balancing can be achieved at each
electrode even if the pulses have different amounts of charge. As
shown, the first two cathodic pulses 112 have an amplitude of
-0.4I, while the last cathodic pulse 112 has an amplitude of -0.2I.
The total charge of the cathodic pulses 112 is again -Q=-I*PW.
While this is charge balanced with the anodic pulse 110, note that
the cathodic pulses 112 may not all have the same therapeutic
efficacy. For example, assume that it is known in a particular
tissue that an effective anodic current is 2.5 times an effective
cathodic current. The cathodic pulses 112 at -0.4I would then have
the same efficacy as the anodic pulse 110 at +I (i.e., 1/0.4=2.5).
The last cathodic pulse 112 with amplitude -0.21 may be less
effective, but this can be tolerable to arrive at a charge balanced
solution. Alternatively, and as shown in dotted lines, the last
cathodic pulse 112 can also have the same amplitude of -0.4I as the
other pulses 112, and hence may be as therapeutically effective,
but 1/2 the pulse width to also arrive at a charge balanced
solution.
[0076] It is not strictly necessary that each pulse packet 115 have
only one anodic pulse 110. Assume for example that an effective
anodic current is 1.5 times an effective cathodic current. In FIG.
10, a pulse packet 115 thus includes two anodic pulses 110 of
amplitude +I, and three cathodic pulses 112 of amplitude -2/3I.
These pulses 110 and 112 should have the same therapeutic
effectiveness (i.e., 1/[2/3]=1.5). Assuming in this example that
the pulses widths of pulses 110 and 112 are the same, the sum of
the charge of the anodic pulses 110 (2*+I*PW) is equal and opposite
to the sum of the charge of the cathodic pulses 112 (3*-2/3I*PW),
and so the pulses 110 and 112 are charge balanced within each
packet 115. Again, the order of the anodic pulses 110 and the
cathodic pulses 112 within a packet 115 can be modified, and the
order need not be the same in each of the packets 115.
[0077] FIG. 11 shows applicability of the disclosed technique when
more than one lead-based electrode 16 is selected for monopolar
stimulation along with the case electrode Ec. This can be useful
because selection of more than one lead-based electrode allows for
the formation of a virtual electrode or virtual pole between the
two selected electrodes, as is known. See, e.g., U.S. Provisional
Patent Application Ser. No. 62/598,114, filed Dec. 13, 2017.
[0078] In this example, two electrodes (e.g., E1 and E2) are
selected in addition to the case electrode Ec. Each electrode E1
and E2 receives of the same current: +1/2I during anodic pulses
110, and -1/6I during cathodic pulses 112. Note however that
electrodes E1 and E2 do not need to share current equally: for
example, E1 may receive 75% of the current (forming pulses 110 and
112 with amplitudes of +3/4I and -1/4I), with E2 receiving the
remaining 25% (forming pulses 110 and 112 with amplitudes of +1/4I
and -1/12I). The total current from E1 and E2 equals the opposite
current at Ec at any point in time, ensuring no net charge
injection into the tissue. Further, the charge at each electrode E1
and E2 is charge balanced between the anodic pulse 110 (+1/2Q) and
the cathodic pulses 112 (-1/2Q).
[0079] FIG. 12 provides a different example in which anodic pulses
116 are not actively driven (e.g., by the DACs in stimulation
circuitry 28; FIG. 3), but are instead passively formed using
passive recovery switches 41.sub.i. Cathodic pulses 112 are
actively driven (28; FIG. 3) as before, followed by the passive
anodic pulse 116 at the end of the packet 115. The circuit diagram
in FIG. 12 illustrates generation of the passive anodic pulse 116.
After the cathodic pulses 112, capacitors C1 and Cc 38 coupled to
the electrodes E1 and Ec would be charged (Vc1, Vcc) with the
polarities as shown. When the passive recovery switches 41.sub.1
and 41.sub.c are closed during the passive anodic pulse (118), thus
shorting electrode nodes e1 and ec 39 to the Vbat reference
voltage, equilibration of the charge on these capacitors will cause
a current flow from E1 to Ec through the patient's tissue, R. Given
the R-C nature of this circuit, the current during the passive
anodic pulse 116 will exponentially decay. Note that the pulse
widths of the cathodic pulses 112 and the passive anodic pulse 116
can be different (e.g., PWa and PWb). In particular, it may be
useful that the pulse width PWb of the passive anodic pulse 116
(i.e., the duration of 118) be long enough to allow the charge
across the capacitors to exponentially decay back to 0 Volts.
However, this is not strictly necessary, as the charge of the
cathodic pulse 112 can be modified to, in sum, equal the charge
dissipated during the passive anodic pulse 116 so that charge is
once again balanced, with the sum of the charge of the cathodic
pulses 112 (-Q) equaling the opposite charge of the passive anodic
pulse 116 (+Q).
[0080] To this point in the application, it has been assumed that
stimulation occurs using monopolar stimulation, with one of the
selected electrodes comprising the conductive case electrode Ec.
However, this is not strictly necessary. FIG. 13 provides an
example using bipolar stimulation in which two lead-based
electrodes 16 are selected for stimulation, such as E1 and E2.
[0081] Although not illustrated, FIG. 13 further suggests how
monopolar stimulation can occur without use of the case electrode
Ec. As FIG. 11 illustrated earlier, a current can be shared between
two electrodes 16--e.g., E1 and E2. In FIG. 13, pseudo-monopolar
simulation can thus be created by sharing a return current
(normally flowing to Ec) between the remaining electrodes E2-E32.
Sharing the current at electrodes E2-E32 provides in sum a
large-area return, akin to the case electrode Ec. In other words,
E1 as a selected active electrode can provide pulses 110 and 112 as
shown, with E2-E32 sharing the return current. Further, the return
current can be shared between E2-E32 and the case electrode Ec.
[0082] It is not strictly necessary that the anodic and cathodic
pulses 110 and 112 all comprise therapeutically-significant pulses.
Consider FIG. 14, which provides anodic pulses 110 with an anodic
current of +I (110) and five cathodic pulses 150 with a cathodic
current of -1/5I (150). In this circumstance, and depending on the
neural tissue at issue, the cathodic current may be of too low an
amplitude to recruit neural elements, and thus will have little or
no therapeutic effect. Such cathodic pulses 150 can nonetheless
still be provided for the purpose of charge balancing at each
electrode. In effect, only the anodic pulses 110 are
therapeutically effective, with the frequency f of therapy thus
being dictated by the timing between the anodic pulses 110.
[0083] The anodic and cathodic pulses 110 and 112 do not have to
occur at a constant frequency, f This is shown in FIG. 15, where
the anodic pulse 110 and the first cathodic pulse 112 are separated
by a time period T1; the first and second cathodic pulses 112 are
separated by T2; the second and last cathodic pulses 112 are
separated by T3; and the last cathodic pulse 112 is separated from
the anodic pulse 112 in the next packet 115 by T4.
[0084] FIG. 16 provides another example in which the packets 115
comprise a single cathodic pulse 112 and a number of anodic pulses
110 at lead-based electrode E1. Pulses of this nature would be
useful in tissues that require a higher cathodic current and a
smaller anodic current to be therapeutically effective.
[0085] While beneficial that the anodic and cathodic pulses 110 and
112 be charge balanced at each electrode and in each packet 115,
this is also not required in all useful implementations. For
example, in FIG. 17, the cathodic currents of the cathodic pulses
112 have been changed to -0.4I. In this circumstance, the anodic
pulse 110 (+Q) is not charge balanced with the cathodic pulses 112
(-1.2Q) in each packet 115, as evidenced by the remaining voltage
Vc1 and Vcc (119) on DC-blocking capacitors C1 and Cc 38 (FIG. 3)
after the issuance of the last cathodic pulse 112 in the packet
115. Nonetheless, this may be acceptable. First, it may be the case
that an effective anodic current +I is 2.5 times an effective
cathodic current, making -0.4I a logical choice for the cathodic
current, even though this results in charge imbalanced pulses in
each packet 115. Further, charge imbalance may be addressed in
other ways. For example, the extra -0.2Q of charge may be passively
recovered during periods 114 as discussed earlier, thus returning
Vc1 and Vcc to zero (117) before the start of the next packet
115.
[0086] FIG. 18 shows how charge imbalanced packets 115 can be used
to provide a charge-balanced solution at each electrode over the
sum of a plurality of packets. Shown are two packets 115a and 115b.
In both packets 115a and 115b, the anodic pulse 110 has a charge of
+Q=+I*PW. In Packet 115a, there are two cathodic pulses 112, each
having a pulse width of PW, and a cathodic current of -0.6I.
Therefore, in sum, the two cathodic pulses 112 in packet 115a have
a total charge of -1.2Q, and thus packet 115a is charge imbalanced
at electrode E1 (with a net charge of -0.2Q). Such charge imbalance
is evidenced by the residual voltage Vc1 and Vcc (119) remaining on
the DC-blocking capacitors C1 and Cc after the last cathodic pulse
112 in packet 115a. In packet 115b, there are again two cathodic
pulses 112, each having a pulse width of PW, but a cathodic current
of -0.4I. Therefore, in sum, the two cathodic pulses 112 in packet
115b have a total charge of -0.8Q, and thus packet 115b is charge
imbalanced at electrode E1 (with a net charge of +0.2Q).
Nonetheless, over the span of packets 115a and 115b, the pulses 110
and 112 are balanced at each electrode. Such charge balance between
the packets 115a and 115b is evidenced by the fact that the voltage
Vc1 and Vcc (117) remaining on the DC-blocking capacitors C1 and Cc
after the last cathodic pulse 112 in packet 115b is zero.
[0087] FIGS. 19A and 19B show particular utility to the use of
charge imbalanced packets 115. In FIG. 19A, each packet 115
includes an anodic pulse 110 of charge +Q, and three cathodic
pulses 112. However, the charge of the cathodic pulses 112 in each
packet 115 are varied by adjusting their pulse widths (although as
explained earlier, their amplitudes could also be changed).
[0088] The cathodic pulses 112 in first packet 115a provide a total
charge of -0.6Q, with a net charge in packet 115a of +0.4Q. As
shown in the graphs of Vc1 and Vcc, this leaves a charge (voltage)
on the DC-blocking capacitors C1 and Cc, and given the polarity of
these voltages, a current 155 will flow from Ec to E1, as shown in
the circuit diagram. As described in U.S. patent application Ser.
No. 16/210,814, filed Dec. 5, 2018, this current 155 comprises a
pseudo-constant DC current which can act even during quite periods
between the pulses 110 and 112 to assist in the recruitment of
neural elements. The cathodic pulses 112 in second packet 115b
provide a total charge of -0.8Q, with a net charge in packet 115b
of +0.2Q. This increases Vc1 and Vcc further, and increases the
current 155 flowing from Ec to E1.
[0089] The cathodic pulses 112 in third and fourth packets 115c and
115d provide a total charge of -Q, and so are balanced with the
anodic pulses 110. Vc1 and Vcc will not increase further but remain
elevated, which allows current 155 to stabilize at a higher
level.
[0090] The cathodic pulses 112 in fifth and sixth packets 115e and
115f exceed the charge of the anodic pulses 110. Thus, the cathodic
pulses 112 in packet 115e have a total charge of -1.2Q, and so
packet 115e has a net charge of -0.2Q. This causes Vc1 and Vcc to
fall, thus establishing current 155 at a lower level. The cathodic
pulses 112 in packet 115f have a total charge of -1.4Q, and so
packet 115f has a net charge of -0.4Q. This causes Vc1 and Vcc to
fall further to zero, and therefore current 155 is brought back to
zero.
[0091] Notice that the total net charge between the packets
115a-115f is zero: anodic pulses 110 provide +6Q, while cathodic
pulses 112 in sum provide -6Q. Nonetheless, providing charge
imbalanced packets can allow a recruitment current 115 to flow. If
it is desired to have current flow in the other direction--from
electrode E1 to the case electrode Ec, the charge imbalance in each
packet simply needs to be modified. That is, packets 115a and 115b
can be established to provide a net negative charge, and packets
115e and 115f can be established to provide an offsetting net
positive charge.
[0092] FIG. 19B shows the same effect as FIG. 19A, but with charge
imbalance realized in each packet 115 in a different manner.
Specifically, charge imbalance is achieved in FIG. 19B by altering
the number of cathodic pulses 112 in each packet. It is assumed in
FIG. 19B that each cathodic pulse 112 has a charge at E1 of -0.2Q.
Three cathodic pulses 112 are provided in packet 115a, for a total
charge of -0.6Q, and a net charge in packet 115a of +0.4Q. Four
cathodic pulses 112 are provided in packet 115b, for a total charge
of -0.8Q, and a net charge in packet 115b of +0.2Q. Five cathodic
pulses 112 are provided in packets 115c and 115d, for a total
charge of -Q, and a net charge in packets 115c and 115d of zero.
Six cathodic pulses 112 are provided in packet 115e, for a total
charge of -1.2Q, and a net charge in packet 115e of -0.2Q. Seven
cathodic pulses 112 are provided in packet 115f, for a total charge
of -1.4Q, and a net charge in packet 115f of -0.4Q. This operates
to the same effect as the pulses in FIG. 19A.
[0093] The various waveforms illustrated to this point can be
combined in different manners, even if such combinations are not
illustrated in the figures. For example, the location of anodic and
cathodic pulses 110 and 112 can be switched in a packet (FIG. 7B,
7C); the cathodic pulses can be of different shapes but of the same
or different charge (FIGS. 8 and 9); more than one anodic pulse 110
can be used (FIG. 10); more than one lead-based electrode can be
used along with the case electrode (FIG. 11); the anodic pulse can
be passive (FIG. 12); the case electrode Ec need not be used (FIG.
13); cathodic pulses 150 need not be therapeutic (FIG. 14); the
anodic and cathodic pulses 110 and 112 can occur at different
frequencies (FIG. 15); a single cathodic pulse 112 can be used with
many anodic pulses (FIG. 16); the anodic and cathodic pulses 110
and 112 need not be charge balanced within a packet 115 (FIG. 17);
but a plurality of imbalanced packets can in sum be charge balanced
(FIGS. 18-19B). It is not practical to illustrate all of these
possible combinations, but it should be understood that any
combination of these techniques can be used in a practical
implementation and are within the scope of this disclosure.
[0094] FIG. 20 shows a Graphical User Interface (GUI) 120 which can
be used to program an IPG or ETS to provide the waveforms described
earlier. GUI 120 may be provided on an external device, such as the
external controller 60 or clinician programmer 70 of FIG. 5. One
skilled in the art will understand that the particulars of the GUI
120 will depend on where the external device's software is in its
execution, which may depend on the GUI selections the clinician or
patient has previously made. The instructions for GUI 120 can be
stored on a non-transitory computer readable media, such as a solid
state, optical, or magnetic memory, and operable within the control
circuitry of the relevant external device.
[0095] FIG. 20 shows the GUI 120 at a point allowing for the manual
setting of stimulation parameters for the patient. A stimulation
parameters interface 122 is provided in which specific stimulation
parameters can be defined for a stimulation program. In particular,
interface 122 may comprise a means for setting monopolar
stimulation in which the case electrode Ec is selected as an active
electrode, although this isn't required. Adjustable settings for
stimulation parameters are shown, including the amplitude I.sub.A
of the anodic pulses 110 and amplitude I.sub.C of the cathodic
pulses 112, their frequency f, and their pulse width PW. It is
assumed in this example that the pulse widths PW of the anodic and
cathodic stimulation pulses 110 and 112 will be the same (e.g.,
FIG. 7A), although as discussed earlier this isn't necessary, and
instead the pulse width of each can be specified in the GUI 120.
Means can also be provided for defining the packets 115 of anodic
and cathodic pulses 110 and 112, including the number of each. As
shown, an option may be provided to allow the charge to be
equalized at the selected electrodes and within each packet 115.
Note that this may involve automatic computation or adjustment of
the other stimulation parameters. For example, if two anodic pulses
110 and three cathodic pulses 112 are specified, the control
circuitry of the external device may set the anodic and cathodic
currents I.sub.A and I.sub.C to achieve charge balance within each
packet 115 (see FIG. 10). An option may also be provided to allow
the anodic pulse 110 to comprise a passive anodic pulse, as
described earlier with respect to FIG. 12. If this option is
selected, anodic current I.sub.A may be set to a "not applicable"
value. FIG. 20 is merely one example by which the waveforms
described earlier can be defined; more complicated user interface
aspects not shown can be provided to allow for the programming of
the waveforms in their various alternatives as previously
described.
[0096] Stimulation parameters relating to the electrodes 16 are
made adjustable in an electrode parameter interface 124. Electrodes
are manually selectable in a leads interface 126 that displays a
graphical representation of the electrode array 17 or 17' (one or
more permanent or trial leads) that has been implanted in a
particular patient (a paddle lead 19 is shown as one example). A
cursor 128 (or other selection means such as a mouse pointer) can
be used to select a particular electrode in the leads interface
126. Buttons in the electrode parameter interface 124 allow the
selected electrode (including the case electrode, Ec) to be
designated as an anode, a cathode, or off (The case electrode Ec
may also be automatically selected if monopolar stimulation is to
occur). The electrode parameter interface 124 further allows the
amount of the current that each selected electrode will receive to
be specified in terms of a percentage, X. This was explained
earlier with reference to FIG. 11, which shows how current could be
split between electrodes E1 and E2, with each receiving 50%. Note
that GUI 120 provides a relatively simple manner for defining the
pulses described earlier.
[0097] FIG. 21 shows an IPG or ETS capable of forming the pulses as
specified by the GUI 120 of the external device. As discussed in
the Introduction, the stimulation parameters entered from the GUI
120 can be wirelessly transmitted by the external device 60 or 70
to an antenna in the IPG or ETS, including the anodic and cathodic
amplitudes I.sub.A and I.sub.c, pulse frequency f, pulse width(s)
PW, the selected electrodes, etc. The stimulation parameters, once
wirelessly received, are provided to control circuitry 140. Control
circuitry 140 may comprise a microcontroller for example, such as
Part Number MSP430, manufactured by Texas Instruments, which is
described in data sheets at
http://www.ti.com/lsds/ti/microcontroller/16-bit_msp430/overview.page?DCM-
P=MCU_other& HQS=msp430. The control circuitry 140 more
generally can comprise a microprocessor, Field Programmable Grid
Array, Programmable Logic Device, Digital Signal Processor or like
devices. Control circuitry 140 may also be based on well-known ARM
microcontroller technology. Control circuitry 140 may include a
central processing unit capable of executing instructions, with
such instructions stored in volatile or non-volatile memory within
or associated with the control circuitry. Control circuitry 140 may
also include, operate in conjunction with, or be embedded within an
Application Specific Integrated Circuit (ASIC), such as described
in U.S. Patent Application Publications 2008/0319497, 2012/0095529,
2018/0071513, or 2018/0071520, which are incorporated herein by
reference. The control circuitry 140 may comprise an integrated
circuit with a monocrystalline substrate, or may comprise any
number of such integrated circuits operating as a system. Control
circuitry may also be included as part of a System-on-Chip (SoC) or
a System-on-Module (SoM) which may incorporate memory devices and
other digital interfaces.
[0098] In FIG. 21, the control circuitry 140 includes pulse logic
142, which receives the stimulation parameters and forms various
control signals 144 for the stimulation circuitry 28. Such control
signals 144 specify the timing and polarity of the stimulation
pulses appearing at each of the selected electrodes, as well as the
amplitude of the current each selected electrode will provide.
[0099] Although particular embodiments of the present invention
have been shown and described, it should be understood that the
above discussion is not intended to limit the present invention to
these embodiments. It will be obvious to those skilled in the art
that various changes and modifications may be made without
departing from the spirit and scope of the present invention. Thus,
the present invention is intended to cover alternatives,
modifications, and equivalents that may fall within the spirit and
scope of the present invention as defined by the claims.
* * * * *
References